Many buildings have vents which provide routes for exchange, ventilation, circulation and/or movement of gas through the building envelope. Such gases may comprise air or water vapour, for example. Buildings may have ventilation systems, which take in “fresh” air from outside of the building and expel “stale” air from inside the building. Fresh air may be taken into a building or stale air may be expelled from a building through one or more vents. Some buildings incorporate other systems and/or apparatus, such as air conditioning systems, range hoods and forced air clothes dryers, which require gas flow between the inside and outside of a building.
Typically, a vent is associated with a conduit which conveys gas towards or away from the vent. A vent typically comprises a vent passageway in fluid communication with the associated conduit to provide a means for gas flow through the building envelope. Vents may provide a number of additional functions. For example, vents may comprise weatherproofing features to minimize the amount of moisture leakage into the building or the building layers. Vents may also provide a more aesthetically pleasing terminus for their associated conduits.
There are many vent designs known in the art. For example:                Canadian patent No. 2,062,907 (Sirjoo) discloses a vent incorporating an adjustable screw cap vent cover which extends outwardly from the external wall of a building and which is adjustable to permit air flow through the vent when the cap is open and to prevent air flow through the vent when the cap is closed; and        Canadian patent No. 2,357,531 (Myint) shows a security air vent which allows for the flow of air, but which comprises a screen having S-shaped structural members for preventing the back flow of solids or liquids into the associated building aperture.        
Some vents comprise vent covers which extend outwardly from the exterior surface of the building. Such vent covers may provide weatherproofing for the vent and may also provide desirable aesthetics. Vents and vent covers may be formed in a single unitary construction.
Vents are preferably sized and shaped such that they are easily mounted to the building structure and easily coupled to their associated conduits. Typically, a vent comprises a flange or the like, which is sized and shaped to engage its associated conduit. Where vents and vent covers are made from a single unitary construction, a separate vent and vent cover combination is required for each size and shape of conduit.
Vents may incorporate dampers to control the flow of gases and/or other materials through the vent. Typically, a damper is formed from a flat (i.e. planar) piece of material that is hingeably mounted to permit flow of gas through the vent in a desired direction and to restrict flow of gas through the vent in the opposing direction. Some dampers undesirably restrict the flow of gas in the desired direction.
Some vents (or vent covers) comprise screens. Typically, such screens are integrally formed with the vent or are attached to the vent using fasteners, such as staples, screws, rivets or the like. Screens help to prevent debris from accumulating in the vent and from potentially entering into the building interior. As screens are typically located near the outermost ends of vents, there is a considerable likelihood for a screen to be damaged or to weaken over time because of exposure to the elements. Replacement of a screen that is integrally formed with a vent component requires replacing the entire vent component and may require removal of outer building layers. Replacement of a screen that is attached to a vent component using fasteners requires removing and replacing the fasteners which can damage the body of the vent component.
There is a general desire to provide vents which ameliorate at least some of the aforementioned or other disadvantages of existing vents.